Sunday, May 5, 2013

Time Is Real; Otherwise, How Can "Now" Even *Seem* Special

It has been argued that claiming time does not exist, or at least that it has unique properties as a dimension, is that this necessarily destroys the possibility of causality. This is often known as eternalism or the conception of a block universe and the conclusion about causality is discussed most notably by Julian Barbour. Not all time-deniers are also causality-deniers, but Barbour (and I, here) claim that in order to be consistent, they should be. But in contrast to Barbour, I take this destruction of casuality as a reductio ad absurdum of the claim that time is not real. That is, if you think causality is real, then so must time in some sense be real. (Lee Smolin makes a much more aggressive and detailed argument about the nature of time and causality in Time Reborn.)

A "common-sense" objection to the time-deniers is that time appears to exist; therefore, it does. The time-deniers' standard response to this (or deniers of time-as-unique-kind-of-dimension deniers) is that time is an illusion created by our limited, provincial nervous systems; and that the in-principle endlessly extensible propositional systems we are creating to understand the universe, like physics, are showing us the true picture, beyond our distorted common-sense.

A further retort to the time-deniers' response is that this illusion of time could not exist in the first place if there were not something special about "now". In a true block universe, all moments are equivalent. How can there be a now at all? Ignorance of the rest of the block universe in favor of this one progressing point should not be possible.

Words to Live By

"...there is good and bad speculation, and this is not an unparalleled activity in science...Those scientists who have no taste for this sort of speculative enterprise will just have to stay in the trenches and do without it, while the rest of us risk embarrassing mistakes and have a lot of fun." - Dan Dennett